Modular Actuator for Subsea Valves and Equipment, and Methods of Using Same

ABSTRACT

The present invention is directed to a modular actuator for subsea valves and equipment, and various methods of using same. In one illustrative embodiment, the actuator includes a hydraulic actuator, at least one housing and a self-contained hydraulic supply system positioned within the at least one housing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally directed to the field of actuators,and more particularly to a modular actuator for subsea valves andequipment, and various methods of using same. In one illustrativeexample, the present invention is directed to a system for controllingan actuator for a downhole safety valve in a subsea Christmas tree.

2. Description of the Related Art

The production from a subsea well is controlled by a number of valvesthat are assembled into a Christmas tree. The actuation of the valves isnormally dependent upon hydraulic fluid to operate hydraulic actuatorsfor the valves and is therefore entirely dependent upon an externalsource for the supply of pressurized hydraulic fluid. Hydraulic power isnormally supplied through an umbilical running from a station located ona vessel on the surface or, less common, from a land based station.Usually the actuators are controlled by pilot valves housed in a controlmodule located at or near the subsea installation, the pilot valvesdirecting the supply of hydraulic fluid to each actuator, as dictated bythe need for operation. The pilot valves may be operated by electricmeans and such a system is therefore called an electro-hydraulic system.

The design of actuators and valves for subsea wells are dictated bystringent demands on the standard and function for these valves, becauseof the dangers of uncontrolled release of hydrocarbons. A typical demandis that these valves must be failsafe closed, meaning that they mustclose upon loss of power or control. The only practical means today insubsea environments is to use springs that are held in the compressedstate by the hydraulic pressure, keeping the valve open, and will bereleased in the event of loss of hydraulic pressure, thus closing thevalve. The spring force needed to close a valve is dependent upon bothwell pressure and ambient pressure, with larger ambient pressuredemanding larger springs.

For the control of subsea wells, a connection between the well and amonitoring and control station must be established. This station caneither be located in a floating vessel near the subsea installations orin a land station a long distance away. Communication between thecontrol station and the subsea installation is normally provided byinstalling an umbilical between the two points. The umbilical containslines for the supply of hydraulic fluid to the various actuators in orby the well, electric lines for the supply of electric power and signalsto various monitoring and control devices and lines for signals to passto and from the well. This umbilical is a very complicated and expensiveitem, costing several thousand dollars per meter.

It would therefore be very cost-saving to be able to eliminate theumbilical. Proposals have been made to use electrically operatedactuators for subsea valves instead of the traditional hydraulicactuators, see for example U.S. Pat. Nos. 5,497,672 and 5,984,260.However, this entails the installation of completely new actuators,resulting that it is not possible to retrofit a hydraulic system with anelectric actuator.

EP Patent Application No. 1209294 discloses an electro-hydraulic controlunit with a piston/cylinder arrangement with the piston dividing thecylinder into two chambers, a fluid connection between the two chambersand a valve to configure the fluid flow such that pressureized hydraulicfluid only may flow in one direction, but not in both directions.

U.S. Pat. No. 6,269,874 discloses an electro-hydraulic surfacecontrolled subsurface safety valve actuator that comprises anelectrically actuated pressure pump and a dump valve that is normallyopen so that if power fails, the pressure is released and the safetyvalve closes.

The present invention is directed to an apparatus for solving, or atleast reducing the effects of, some or all of the aforementionedproblems.

SUMMARY OF THE INVENTION

The present invention is directed to a modular actuator for subseavalves and equipment, and various methods of using same. In oneillustrative embodiment, the actuator comprises a hydraulic actuator, atleast one housing and a self-contained hydraulic supply systempositioned within the at least one housing.

In another illustrative embodiment, the actuator comprises a hydraulicactuator, at least one housing and a plurality of components positionedwithin the at least one housing, the components comprising aself-contained hydraulic supply system and a control system to controldelivery of a high pressure hydraulic fluid produced by theself-contained hydraulic supply system.

In yet another illustrative embodiment, the actuator comprises ahydraulic actuator, at least one housing and a self-contained hydraulicsupply system positioned within the at least one housing, theself-contained hydraulic supply system comprising a pump driven by anelectrical motor, at least one fluid reservoir and a control/vent valve.

In a further illustrative embodiment, the actuator comprises a hydraulicactuator, at least one housing and a self-contained hydraulic supplysystem positioned within the at least one housing, the self-containedhydraulic supply system comprising a pump driven by an electrical motor,at least one fluid reservoir and a control/vent valve. The actuatorfurther comprises a control system positioned within the at least onehousing to control delivery of a high pressure hydraulic fluid producedby the self-contained hydraulic supply system and a self-containedsource of electrical power positioned within the at least one housing,wherein the self-contained source of electrical power is the primarysource of electrical power for the modular actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numerals identify like elements, and in which:

FIG. 1 is a schematic depiction of one illustrative embodiment of thepresent invention employed in connection with a subsea valve;

FIG. 2 is another schematic depiction of an alternative embodiment ofthe present invention employed in connection with a subsea equipmentitem;

FIGS. 3 a-3 f describe various aspects of a modular actuator inaccordance with one illustrative embodiment of the present invention;

FIG. 4 is a schematic depiction of an illustrative modular actuator inaccordance with one embodiment of the present invention;

FIG. 5 is a depiction of yet another illustrative embodiment of amodular actuator in accordance with the present invention;

FIG. 6 is a more detailed schematic depiction of one illustrativeembodiment of the present invention in a first working mode;

FIG. 7 is a detailed schematic depiction showing one illustrativeembodiment of the present invention in a fail safe mode;

FIG. 8 is yet another illustrative embodiment of the present inventionemploying an alternative valve arrangement; and

FIGS. 9 a-9 c depict an illustrative embodiment of the present inventionin various operating configurations.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

The present invention will now be described with reference to theattached figures. The words and phrases used herein should be understoodand interpreted to have a meaning consistent with the understanding ofthose words and phrases by those skilled in the relevant art. No specialdefinition of a term or phrase, i.e., a definition that is differentfrom the ordinary and customary meaning as understood by those skilledin the art, is intended to be implied by consistent usage of the term orphrase herein. To the extent that a term or phrase is intended to have aspecial meaning, i.e., a meaning other than that understood by skilledartisans, such a special definition will be expressly set forth in thespecification in a definitional manner that directly and unequivocallyprovides the special definition for the term or phrase.

In the following description, the term fluid line is used to indicate afluid connection between components of the system. It should beunderstood that in various embodiments, the fluid connection betweencomponents may comprise an actual fluid conduit such as a pipe or hose,or the components may be connected directly to each other. Anyconfiguration which allows for fluid communication between components asdescribed below is considered to be within the spirit and scope of theinvention.

In the specification, terms such as “upward” or “downward” or the likemay be used to refer to the direction of fluid flow between variouscomponents of the devices depicted in the attached drawings. However, aswill be recognized by those skilled in the art after a complete readingof the present application, the device and systems described herein maybe positioned in any desired orientation. Thus, the reference to thedirection of fluid flow should be understood to represent a relativedirection of flow and not an absolute direction of flow. Similarly, theuse of terms such as “above,” “below,” or other like terms to describe aspatial relationship between various components should be understood todescribe a relative relationship between the components as the devicedescribed herein may be oriented in any desired position.

Also in the following description, the terms low pressure and highpressure are used to describe various portions of the system. It shouldbe understood that these terms are used in a relative sense. Lowpressure is used to describe the fluid supply and the portions of thesystem in fluid communication with the fluid supply. High pressure isused to describe the fluid which is pressurized by the pump or otherpressure intensifying device, and the portions of the system in fluidcommunication with pump output. The term high pressure is used only toindicate that this portion of the system is at a higher pressurerelative to the fluid supply. The term low pressure is used only toindicate that this portion of the system is at a lower pressure than thepump output. The actual absolute or gauge pressure of the variousportions of the system is irrelevant to the definition of high or lowpressure.

FIGS. 1 and 2 schematically depict illustrative systems 10 employing amodular actuator 16 in accordance with various aspects of the presentinvention. As depicted in FIG. 1, the modular actuator 16 is operativelycoupled to a valve actuator 15 that is operatively coupled to a subseavalve 12 positioned in a flow line or well conduit 14. The valveactuator 15 may be of any type, e.g., a mechanical valve actuator, ahydraulic valve actuator, etc. Thus, the particular type of valveactuator disclosed herein should not be considered a limitation of thepresent invention. In the embodiment depicted in FIG. 2, a plurality ofmodular actuators 16 are operatively coupled to valve actuators 15 that,in turn, are operatively coupled to a item of subsea equipment 18, suchas an illustrative Christmas tree. As will be described more fullybelow, in one illustrative embodiment, the modular actuator 16 of thepresent invention is a self-contained actuator that is adapted toactuate a subsea valve 12 or other similar type component. In theillustrative embodiment depicted in FIG. 2, the plurality of modularactuators 16 are adapted to control a plurality of valves (not shown)positioned internally within the schematically depicted Christmas tree18.

As will be described more fully below, the modular actuator 16 describedherein comprises a self-contained power supply, and it may be readilydecoupled from the valve actuator 15 and removed to the surface.Importantly, in one illustrative embodiment, the modular actuator 16described herein comprises a self-contained hydraulic system that willbe used, at least in part, to actuate the subsea valve 12 or other likeequipment. In accordance with one illustrative aspect of the presentinvention, since the modular actuators 16 described herein employ aself-contained hydraulic system, a supply of high pressure hydraulicfluid from a station location on a surface vessel or from a land-basedstation is not required. Moreover, the modular actuator 16 disclosedherein is configured so that it may be easily coupled and decoupled fromthe subsea equipment, e.g., the valve actuator 15, to which it isattached by a variety of techniques, e.g., by use of an ROV (remotelyoperated vehicle), a diver, etc., and retrieved to the surface asnecessary for repairs.

FIGS. 3 a-3 f depict one illustrative embodiment of the modular actuator16 in accordance with the present invention. In general, the modularactuator 16 comprises a hydraulic actuator and one or more housingportions that are adapted to contain various components of the modularactuator 16, including a self-contained hydraulic supply system. Asdepicted in FIGS. 3 a-3 f, the modular actuator 16 comprises a linearoverride tool 16A and housings 16B, 16C, 16D for housing variouselectrical and hydraulic components, including hydraulic fluid,associated with the modular actuator 16. Although the illustrativeembodiment depicted herein comprises three separate housings 16B, 16C,16D, those skilled in the art, with the benefit of the presentdisclosure, will understand that the modular actuator 16 may compriseone or more housings to house the various components of the systemdescribed herein. Thus, the present invention should not be consideredas limited to the illustrative embodiments depicted herein.

In the depicted embodiment, an interface device 17 may be providedbetween the modular actuator 16 and the valve actuator 15. Even morespecifically, in the illustrative example depicted herein, the interfacedevice 17 may comprise a spool having a first flange 17A, a secondflange 17B and a travel indicator 17C. The first flange 17A is adaptedto be coupled to the valve actuator 15. Typically, the interface device17 may be coupled to the valve actuator 15 at the time the subsea systemis placed into service. Thereafter, the modular actuator 16 may beoperatively coupled to the flange 17B when desired or needed, as will bedescribed more fully below. As will be recognized by those skilled inthe art after a complete reading of the present application, theinterface device 17 may take a variety of shapes and forms. For example,in one illustrative embodiment, the interface device 17 may be designedin accordance with the teachings of a standard entitled “Design andOperation of Subsea Production Equipment Systems,” ISO/FDIS13628-8:2000(E), pp. 39-42. In other embodiments, a separate interfacedevice 17 need not be provided. That is, to the extent an interface isprovided, it may be provided as an integral part of either the valveactuator 15 or the modular actuator 16.

As to more specifics, the modular actuator 16 may comprise a hydraulicfluid reservoir 16D, an ROV handle 16E, an ROV handle 16F, a shaft 16Gand a plurality of seals 16H. The modular actuator 16 is provided with arecess 161 that is adapted to be positioned around the flange 17B of theinterface device 17. A plurality of anti-rotation devices 16J, e.g.,studs or nuts, are provided to reduce or prevent rotation of the modularactuator 16 relative to the interface device 17.

FIGS. 3 a-3 c depict the modular actuator 16 as it is being lowered ontothe flange 17B of the interface device 17. An ROV may be used to installthe modular actuator 16. As indicated previously, in one illustrativeembodiment, the interface device 17 is attached to the valve actuator 15as part of the initial installation process of the subsea system. Anynumber of valves of a particular subsea system may be provided with suchan interface device 17 such that a modular actuator 16 may beoperatively coupled to such valves when needed. More specifically, inone illustrative embodiment, an ROV (remotely operated vehicle) or otherlike device may be employed to position the modular actuator 16 in aposition where it may operate a subsea devices, such as a valve. Themodular actuator 16 may be lowered onto the flange 17B through use of anROV that grasps ROV handle 16E. FIG. 3 c depicts the modular actuator 16in the fully landed position. The recess 16I is sized such that themodular actuator 16 fits securely around the flange 17B. Theanti-rotation devices 16J prevent or reduce rotation of the modularactuator 16 relative to the interface device 17 and the valve actuator15. When the modular actuator 16 is in a horizontal position, the weightof the modular actuator 16, along with the closeness of fit between therecess 16I and the flange 17B, tend to secure the modular actuator 16 inposition. With reference to FIG. 3E, when the modular actuator 16 isactivated or stroked, the shaft 16G will extend into the bore of theinterface device 17 thereby insuring that the modular actuator 16remains in place irrespective of whether the valve actuator 15 ispositioned horizontally, vertically, or at any other angle. Additionaloperational aspects of the modular actuator 16 will be described morefully below.

Illustrative examples of the associated electrical and hydrauliccontrols that may be employed with the modular actuator 16 are depictedin FIG. 3 f. As shown therein, the system comprises an accumulator 16K,a pump 16L, driven by an electric motor 16M, a check valve 16N, pressuresensors 16O, 16P, 16Q, a filter 16R and a solenoid valve with springreturn 16S. In one illustrative embodiment, the solenoid valve 16S maybe a normally closed valve, as depicted in FIG. 3 f. When the solenoidvalve 16S is actuated and moved to its “open” position, the pump 16L maybe activated to increase the pressure of the hydraulic fluid supplied tothe chamber 16T. In turn, this causes the shaft 16G to move to the rightin FIG. 3 f, as indicated by the arrow 16U. The end 16W of the shaft 16Gengages the end 15B of the shaft 15A (see FIG. 3 e) of the valveactuator 15 when the shaft 16G moves in the direction of the arrow 16U.The pump 16L continues to operate until the pressure on both sides ofthe solenoid valve 16S is substantially equal, as determined by thepressure sensors 16P, 16Q. At that point, the shaft 16G is fullyextended and the pump 16L may be stopped.

When the solenoid valve 16S is de-energized, e.g., in an emergencysituation, the solenoid valve 16S returns (due to its spring return) toits closed position, as depicted in FIG. 3 f. With the solenoid valve16S in the closed position, the high pressure hydraulic fluid in thechamber 16T is free to return to the accumulator 16K, and the shaft 16Gis free to travel to the left in FIG. 3 f, as indicated by the arrow16V, until it reaches its fully retracted position. A force, such as aspring force, may be supplied to urge the shaft 16G to its fullyretracted position. Such a force may be supplied by, for example, areturn spring on a subsea safety valve. A portion of the shaft 16G willremain positioned within the bore of the interface device 17 even whenthe solenoid valve 16S is in its closed position (as shown in FIG. 3 f).In one embodiment, to fully retract the shaft 16G from inside the boreof the interface device 17, an ROV is employed to grasp and pull on thehandle 16F (see FIG. 3 e). Once the shaft 16G has been completedisengaged from the bore of the interface device 17, the modularactuator 16 may be removed by use of an ROV that grasps the handle 16E.An ROV may be used to open or close a needle valve 16Y (see FIG. 3F),via handle 16X (see FIG. 3 e), to vent the system if the need arises. Atravel indicator 17C may be used to determine the movement of the shaft15A. The travel indicator 17C is secured to the shaft 15A by a bolt 17D(see FIG. 3 e). The bolt 17D is free to travel within the groove 17E.

FIG. 4 is a schematic depiction of the various components that may beincluded in one illustrative embodiment of the modular actuator 16disclosed herein. As shown in FIG. 4, a variety of components arepositioned in a one or more housings, generally indicated by the number20, associated with the modular actuator 16. The exact number ofhousings and the location of various components of the system describedherein may vary depending upon the particular application. Of course,the modular actuator 16 will ultimately be operatively coupled to anillustrative valve actuator 15. In general, the modular actuator 16comprises, in one illustrative embodiment, a fluid reservoir-accumulator44, a pressure intensifier 47, a check valve 34, a control/vent solenoidvalve 40, a battery 54 and a control system 50. A plurality of hydraulicflow lines 45, 36, 48 and 42 are positioned within the housing 20. Themodular actuator 16 further comprises an illustrative electricalconnection 36 that is adapted to mate with a schematically depictedelectrical line 37.

The pressure intensifier 47 schematically depicted in FIG. 4 may becomprised of a variety of devices. The pressure intensifier 47 may beany device or system that employs electrical power to increase thepressure in a fluid. For example, in one embodiment, the pressureintensifier 47 may be a rotary pump driven by a schematically depictedelectric motor 31 shown in FIG. 4. In another illustrative embodiment,the pressure intensifier 47 may also be a reciprocating pump driven byan electric motor (see, e.g., FIGS. 9 a-9 c). In the illustrativeembodiment depicted in FIG. 4, the system within the modular actuator 16is adapted to provide a high pressure hydraulic fluid to a component,such as the illustrative subsea valve 12, to accomplish the desiredpurpose, e.g., to move a valve from a first position to a secondposition.

Electrical power for the electrical components within the housing 20 maybe provide by an electrical line that extends to a surface source ofelectrical power or it may be provided by one or more batteries that arepositioned inside the housing 20 or otherwise located proximate to themodular actuator 16. Moreover, depending upon the particular applicationthe batteries may be the primary source of electrical power for theelectrical components within the housing 20. In one illustrativeembodiment, the battery 54 (see FIG. 4) is positioned in the housing 20and it is the primary source of power for the electrical components ofthe modular actuator 16, e.g., the motor 31, the control system 35, thesolenoid control/vent valve 40, etc. Thus, in this embodiment, themodular actuator 16 also has a self-contained electrical power source.The battery 54 (or groups thereof) may be any of a variety ofcommercially available batteries employed in subsea applications.

Recharging the battery 54 may be accomplished by a substantiallycontinuous trickle charge that is applied to the battery 54.Alternatively, the control system 35 may be employed to monitor thestored charge in the battery 54 and when it reaches a certain minimumallowed level, the battery 54 may be recharged by temporarily couplingit to a full power electrical line. In other embodiments, electricalpower to the electrical components with the housing 20 may be provide bya traditional electrical power line or cable and the battery 54, ifpresent, may serve a traditional back-up role.

If it is desired to replace the battery 54 within the housing 20 of themodular actuator 16, then the modular actuator may be decoupled from thesubsea valve 12 or equipment 18 and taken to the surface. As describedpreviously, an ROV or diver may be employed to decouple the modularactuator 16 from the subsea valve 12 or equipment 18 and transport it tothe surface.

The illustrative control system 50 depicted within the modular actuator16 is adapted to sense various conditions existing within the systemcontained in the modular actuator 16 and take various control actions inresponse thereto, as described more fully below. The control system 35may take a variety of shapes and forms. In one illustrative embodiment,the control system 50 comprises a programmable logic device or amicroprocessor and a memory device for storing a variety of data and/orprograms.

FIG. 5 depicts yet another illustrative embodiment of the modularactuator 16 described herein. Relative to the embodiment depicted inFIG. 4, in the embodiment depicted in FIG. 5, a hydraulic actuator 28(having a shaft or stem 21 and an end interface 27) has been included inthe modular actuator 16. In this illustrative embodiment the interface27 of the hydraulic cylinder 28 may be coupled to any of a variety ofdevices, e.g., a subsea valve, and actuated to open or close such avalve.

FIG. 6 is a more detailed depiction of some of the various components ofthe modular actuator 16 in accordance with one illustrative embodimentof the present invention. For ease of reference many of the componentsshown in FIGS. 1-5 will be shown in FIGS. 6-8 with a corresponding “1”prefix. As shown therein, an actuator 128 has a cylindrical housing 112.A piston 114 is axially movable in the housing, between first and secondpositions. A stem 121 is attached to the piston 114 and extends outsidethe housing 112. An illustrative flange or bracket 122 is provided foroperatively coupling the actuator 129 to a subsea valve (not shown inFIG. 6). In one illustrative embodiment, the actuator 129 is providedwith a handle 124 that enables the actuator 129 to be transported andmounted with an ROV. A linear override tool 120 may also be used formanually moving the piston 114, using an ROV tool. The actuator 129depicted in FIG. 6 may be employed with a modular actuator 16 like theone schematically depicted in FIG. 4. Of course, the actuator 129depicted in FIG. 6 may also be employed with a modular actuator 16 likethe one schematically depicted in FIG. 5, wherein the actuator 129 ispositioned within the housing 20 of the modular actuator 16. Of course,in that case, the actuator 129 may not be provided with a separate ROVhandle 124 or the linear override tool 120.

The piston 114 includes seals 111 to seal the piston 114 against thecylinder. The piston 114 defines first 113 and second 115 (see FIG. 7)chambers in the housing 112. A fluid line 142 connects the secondchamber 115 with a variable volume fluid reservoir-accumulator 144. Inone illustrative embodiment, the fluid in accumulator 144 is at ambientsea pressure. The variable volume accumulator 144 evens out pressuresurges in the return system and also provides for spare fluid capacity,as is well known in the art. A fluid line 145 connects the accumulator144 with the intake side of an illustrative pressure intensifier, e.g.,a pump 147. A stub fluid line with a coupling 143 can be incorporatedinto the fluid line 145, to enable fluid to be replenished and refillthe accumulator 144. A fluid line 136 connects the first chamber 113with the pressure side of pump 147. A one-way valve or check valve 134is installed in fluid line 136, allowing fluid to flow only towardschamber 113.

An additional fluid line 148 interconnects fluid lines 145 and 136. Influid line 148 there is mounted a control-vent solenoid valve 140, thevalve 140 being movable between a closed position (FIG. 7) preventingfluid flow through line 148, and an open position (FIG. 8) allowingfluid flow through line 148. As seen from FIG. 8, when valve 140 is inits open position fluid may flow in either direction between the firstchamber 113 and the second chamber 115. A spring 139 is arranged to biasthe valve 140 towards its open position. A solenoid 138 may beselectively energized to move the valve 140 to its closed position,against the biasing force of the spring 139.

The pump 147 is operated by a motor 131. Pressure and temperaturesensors 127 and 133 are mounted in fluid lines 136 and 145,respectively. A filter unit 146 may be installed in fluid line 145between the pump intake and the fluid supply 144.

The various parts of the unit are in communication with a control module150 through cables 126, 128, 130 and 132. The control module 150 is incommunication with a remote station (not shown) via a cable 152, toreceive power and communication signals therefrom.

In one illustrative embodiment, the motor 131 is a brushless DC motor.Also, in one illustrative embodiment, the control module 150 includes abattery 154 to provide primary power to the motor 131 and the solenoid138. The battery 154 may be trickle-charged from a local power source orfrom a remote location. In this instance, only a small cable would beneeded to charge the battery 154. Alternatively, primary electricalpower may be supplied from a remote location and the battery 154, ifpresent, may merely serve as a traditional back-up source for anemergency supply of electrical power.

FIG. 7 depicts the present invention in a fail safe mode. As showntherein, a subsea valve 212 is adapted to be operated by the actuator129. The valve 212 comprises a valve element 202 connected to a valvestem 204, the valve stem 204 extending into and through a spring housing206. A spring 208 is located in the spring housing 206. The valve stem204 has a spring actuating flange 210 rigidly attached thereto. Thevalve stem 204 terminates in a standard interface mechanism 211. Thepiston stem 121 has at its end a corresponding interface 127, allowingthe valve stem 204 to be operably connected to the piston stem 121.

In FIG. 7, the valve element 202 is depicted in the closed position. Tomove the valve element 202 to its open position, the solenoid 138 isenergized to move the two-way valve 140 to the closed position shown inFIG. 7, against the force of the spring 129. This closes the fluid pathbetween chambers 113 and 115 of the actuator 128. Then the motor 131 isoperated to drive the pump 147, thus transferring fluid from the lowpressure portion of the system (comprising the second chamber 115 andthe accumulator 144) to the first chamber 113 of the actuator 129. Thehigh pressure fluid in chamber 113 displaces the piston 114 to itssecond (extended) position, shown in FIG. 8.

Consequently, this will move the valve stem 204, causing the valveelement 202 to move to its open position (not shown in FIG. 7). Pressuresensor 127 senses the pressure in fluid line 136, and the control module150 cuts power to the motor 131 when the pressure in line 136 issufficient to drive the valve stem 206 against the power of the spring208. One-way valve 134 and two-way-valve 140 prevent high pressure fluidfrom exiting chamber 113, thus ensuring that the valve element 202 isheld in its open position. In moving the valve element 202 to its openposition, the spring 208 is compressed thereby creating a bias returnforce in the spring 208 that will tend to move the valve element 202 toits closed position.

When it becomes necessary to close the valve 202, either electively orin an emergency situation, power to the solenoid 138 is shut off,causing the two-way valve 140 to move to its open position shown in FIG.8 as a result of the biasing force provided by the spring 139. Thisopens the fluid communication path between first 113 and second 115chambers, and blocks or shuts off flow from the pump 147 to the firstchamber 113. Since the pressure now is equalized on each side of thepiston 114, the spring 208 will force the piston 114 and stem 116backwards to its first (retracted) position, and the valve 202 willclose as fluid is transferred to chamber 115 from chamber 113.

FIG. 8 shows a system similar in many respects to the system of FIG. 6.However, in FIG. 8, a flow line 167 extends between chamber 113 of theactuator 129, and a first port of a three-way solenoid valve 160. Asecond port of valve 160 is connected to flow line 136, which is in turnconnected to the output of pump 147. A third port of valve 160 isconnected to flow line 168, which is in turn connected to flow line 145.The valve 160 is biased towards a first, or venting position (not shown)by a spring 161. A solenoid 162 is selectively operable to move valve160 to a second position, as shown in FIG. 8. In the second position,the valve 160 allows fluid communication between the output of pump 147and the first chamber 113. In this position, flow line 168 is blocked.High pressure fluid from the pump 147 is introduced into the chamber 113of the actuator 128, thus driving the stem 121 to its extended positionwhich opens the valve element 202.

When it becomes necessary to close the valve 202, either electively orin an emergency situation, power to the solenoid 162 is shut off,causing the three-way valve 160 to move to its first, or ventingposition. This opens the fluid communication path between first 113 andsecond 115 chambers, and blocks flow from the pump to the first chamber113. Since the pressure now is equalized on each side of the piston 114,the spring 208 will force the piston 114 and stem 121 backwards to itsfirst (retracted) position, and the valve 202 will close as fluid istransferred to chamber 115 from chamber 113.

The solenoid valve 160 is pressure-balanced, as will be clearlyunderstood from FIG. 8. The required biasing force of the spring 161 isvery small, and thus the required holding force of the solenoid 162 maybe correspondingly small.

The modular actuator 16 according to the present invention may be madevery small and compact. It is releasably connected to the valve 212making it easy to replace or retrieve for repairs or maintenance. Thehydraulic portion of the system is entirely self-contained within thehousing 20 of the modular actuator 16. Thus, no external hydraulic linesare necessary—control signals and power are transmitted through a simpleand inexpensive electrical cable arrangement. The modular nature of theactuator 16 also makes it possible to exchange the actuator 16 withother types of actuators, such as an all-electric actuator. It is alsopossible to retrofit the actuator 16 onto a valve which was previouslymanually operated. Once the valve 212 has been fully actuated, theactuator 16 of the present invention requires very little power to holdthe valve in position.

Another exemplary embodiment of a modular actuator 16 in accordance withthe present invention is shown schematically in FIGS. 9 a-9 c. Ahydraulic power unit (HPU) 380 is positioned within the housing 20 ofthe modular actuator 16. For convenience, the illustrative controlsystem 50 and battery 54 are not depicted in FIGS. 9 a-9 c. The unit 380includes a master cylinder 381 with a piston 382 reciprocally movableaxially in the cylinder, thus dividing the cylinder into two chambers383 and 384. The two chambers 383 and 384 are interconnected through abypass line 391, the flow through the bypass being controlled by abypass control valve 390.

In the exemplary embodiment the actuator that moves piston 382 mayconsist of an electric motor with a gearbox and transmission. In theexemplary embodiment, an electric motor 385 is operatively connected toa shaft 386 by a suitable gearbox 375, such that operation of motor 385may precisely control the motion of piston 382. Examples of a suitablemotor 385 and gearbox 375 combination include a Model Number TPM 050sold by the German company Wittenstein. The motor may alternatively be alinear electric motor.

In the well tubing there is mounted a controllable downhole safety valve346, known in the art as an SCSSV (Surface Controlled Subsurface SafetyValve). As is well known in the art, the SCSSV includes a hydrauliccylinder including a “slave” chamber 393. To actuate the SCSSV, chamber393 is pressurized, pushing a piston 394 against the biasing force of aspring 395 to open the valve 346. A fluid line 387 is connected betweenthe slave chamber 393 with an outlet port 398 of an operation controlvalve 388 positioned within the housing 20. A first inlet port 396 ofoperation control valve 388 is connected to fluid line 389, which isconnected to cylinder chamber 383. This arrangement controls the flow offluid from master cylinder 381 to the SCSSV actuator 374. A check valve399 is mounted in line 389, between the operation control valve 388 andthe chamber 383. The check valve 399 allows fluid to flow from chamber383 to chamber 393, but not the reverse.

An accumulator 400, containing a supply of hydraulic fluid, is connectedto the fluid line 387 via line 401, at a point between operation controlvalve 388 and check valve 399. The accumulator 400 provides a buffer forthe high pressure hydraulic fluid, and ensures that the SCSSV will stayopen under normal operating conditions.

A pressure balanced compensator 405 is connected to a second inlet port397 of operation control valve 388 via line 406. A fluid line 408connects compensator 405 with chamber 384 of master cylinder 381. Afluid line 409 connects compensator 405 with a hydraulic coupling 411.The coupling 411 allows hydraulic fluid to be supplied from an externalsource (not shown) so that fluid can be added to the hydraulic system.

Referring to FIG. 9 a, when the motor 385 is energized, the piston 382will move downward in the master cylinder 381. This forces high-pressurefluid through the line 387 to the slave cylinder 393 in the downholevalve actuator 374, with the operation control valve 388 in a first oropen position. On the downstroke, the chamber 384 of master cylinder 381is refilled from compensator 405. Check valve 399 and accumulator 400cooperate to maintain the pressure in the line 387 at a level that willhold the SCSSV valve open. Referring to FIG. 9 b, to close the SCSSVvalve, the operation control valve 388 is shifted to its second orclosed position. In the second position, operation control valve 388allows fluid to flow back up through line 387, through line 406 and backinto compensator 405. In other words, the slave chamber 393 of thedownhole actuator is vented through operation control valve 388 to thelow-pressure system.

The pressure differential across piston 382 will normally force thepiston back to its upper starting position when the motor isde-energized. However, under certain conditions it may be necessary toreset the piston 382 to the upper position. To do this, bypass controlvalve 390 is shifted to a second, or open position, as shown in FIG. 9c. In the second position, bypass control valve 390 allows fluid to flowthrough the bypass line between the two chambers 383 and 384 of themaster cylinder. The electric motor 385 may then be run in reverse inorder to move the piston 12 back to the upper starting position.

Referring to FIG. 9 b, when it is desired to recharge the accumulator400, the operation control valve 388 may or may not be shifted to itssecond position and the motor 385 is energized to drive the piston 382downward in master cylinder 381. A pressure sensor 413 in line 401monitors the pressure in the accumulator 400, making it possible to stopthe motor 385 when desired pressure is reached.

From time to time it may become necessary to replenish the hydraulicfluid in the system, to replace fluid lost due to leaks, for example. Toaccomplish this, an external source (not shown) of hydraulic fluid maybe coupled to the hydraulic coupler 411. Fluid from the external sourcefills the compensator 405 and first chamber 384 of master cylinder 381.By shifting the bypass control valve 390 to its open position (FIG. 9c), fluid may also flow into second chamber 383. Bypass control valve390 may then be moved to the closed position (FIG. 9 b), and piston 382may be moved downwards to recharge the accumulator 400, as previouslydescribed.

The exemplary embodiment of the invention shown in FIGS. 9 a-9 cincludes a high-pressure section, including accumulator 400, which ismaintained at a pressure which is sufficient to operate the SCSSV. Thisembodiment also includes a low-pressure section, including compensator405, which is maintained at a second pressure which is less than thepressure required to operate the SCSSV. The compensator 405 may bepartly filled with an inert gas such as nitrogen, which compensates forpressure differences due to operation of the SCSSV, and which alsoprimes the system for use at various water depths.

By utilizing the exemplary embodiment of the modular actuator 16 shownin FIGS. 9 a-9 c, a standard, hydraulically actuated downholesafety-valve can be used while eliminating the need for a high-pressurehydraulic fluid supply from the surface. Standard downhole safety valveshave a spring failsafe feature so that the valve will close whenpressure is relieved in the system. The valve will therefore also closein the event of a hydraulic system failure. In an emergency the SCSSVcan quickly be closed by shifting operation control valve 388 to itssecond position, thus venting the high-pressure fluid from line 387.

The present invention is directed to a modular actuator for subseavalves and equipment, and various methods of using same. In oneillustrative embodiment, the actuator comprises a hydraulic actuator, atleast one housing and a self-contained hydraulic supply systempositioned within the at least one housing.

In another illustrative embodiment, the actuator comprises a hydraulicactuator, at least one housing and a plurality of components positionedwithin the at least one housing, the components comprising aself-contained hydraulic supply system and a control system to controldelivery of a high pressure hydraulic fluid produced by theself-contained hydraulic supply system.

In yet another illustrative embodiment, the actuator comprises ahydraulic actuator, at least one housing and a self-contained hydraulicsupply system positioned within the at least one housing, theself-contained hydraulic supply system comprising a pump driven by anelectrical motor, at least one fluid reservoir and a control/vent valve.

In a further illustrative embodiment, the actuator comprises a hydraulicactuator, at least one housing and a self-contained hydraulic supplysystem positioned within the at least one housing, the self-containedhydraulic supply system comprising a pump driven by an electrical motor,at least one fluid reservoir and a control/vent valve. The actuatorfurther comprises a control system positioned within the at least onehousing to control delivery of a high pressure hydraulic fluid producedby the self-contained hydraulic supply system and a self-containedsource of electrical power positioned within the at least one housing,wherein the self-contained source of electrical power is the primarysource of electrical power for the modular actuator.

The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. For example, the process steps set forth above may beperformed in a different order. Furthermore, no limitations are intendedto the details of construction or design herein shown, other than asdescribed in the claims below. It is therefore evident that theparticular embodiments disclosed above may be altered or modified andall such variations are considered within the scope and spirit of theinvention. Accordingly, the protection sought herein is as set forth inthe claims below.

1. A modular actuator adapted to be releasably coupled to a subseadevice, comprising: a hydraulic actuator; at least one housing; and aself-contained hydraulic supply system positioned within said at leastone housing.
 2. The modular actuator of claim 1, wherein said subseadevice comprises a valve.
 3. The modular actuator of claim 1, whereinsaid subsea device comprises a Christmas tree.
 4. The modular actuatorof claim 1, further comprising a control system positioned within saidat least one housing to control delivery of a high pressure hydraulicfluid produced by said self-contained hydraulic supply system.
 5. Themodular actuator of claim 1, further comprising a self-contained sourceof electrical power positioned within said at least one housing, whereinsaid self-contained source of electrical power is the primary source ofelectrical power for said modular actuator.
 6. The modular actuator ofclaim 5, wherein said self-contained source of electrical powercomprises at least one battery.
 7. The modular actuator of claim 1,wherein said self-contained hydraulic supply system comprises a pressureintensifier.
 8. The modular actuator of claim 1, wherein saidself-contained hydraulic system positioned within said housing comprisesa pump driven by an electrical motor.
 9. The modular actuator of claim1, wherein said self-contained hydraulic system comprises at least onefluid reservoir and a control/vent valve.
 10. The modular actuator ofclaim 1, wherein said modular actuator further comprises means forreleasably coupling said modular actuator to said subsea device.
 11. Themodular actuator of claim 2, wherein said self-contained hydraulicsupply system is adapted to supply a pressurized fluid employed inactuating said subsea valve.
 12. The modular actuator of claim 3,wherein said self-contained hydraulic supply system is adapted to supplya pressurized fluid employed in actuating a valve within said Christmastree.
 13. The modular actuator of claim 1, wherein said modular actuatoris adapted to be releasably coupled to said subsea device by an ROV. 14.A modular actuator adapted to be releasably coupled to a subsea device,comprising: a hydraulic actuator; at least one housing; and a pluralityof components positioned within said at least one housing, saidcomponents comprising: a self-contained hydraulic supply system; and acontrol system to control delivery of a high pressure hydraulic fluidproduced by said self-contained hydraulic supply system.
 15. The modularactuator of claim 14, further comprising a self-contained source ofelectrical power positioned within said at least housing, wherein saidself-contained source of electrical power is the primary source ofelectrical power for said modular actuator.
 16. The modular actuator ofclaim 14, wherein said self-contained source of electrical powercomprises at least one battery.
 17. The modular actuator of claim 14,wherein said self-contained hydraulic supply system comprises a pressureintensifier.
 18. The modular actuator of claim 14, wherein saidself-contained hydraulic system positioned within said housing comprisesa pump driven by an electrical motor.
 19. The modular actuator of claim14, wherein said self-contained hydraulic system comprises at least onefluid reservoir and a control/vent valve.
 20. The modular actuator ofclaim 14, wherein said modular actuator further comprises means forreleasably coupling said modular actuator to said subsea device.
 21. Themodular actuator of claim 14, wherein said self-contained hydraulicsupply system is adapted to supply a pressurized fluid employed inactuating a subsea valve.
 22. The modular actuator of claim 14, whereinsaid modular actuator is adapted to be releasably coupled to said subseadevice by an ROV.
 23. A modular actuator adapted to be releasablycoupled to a subsea device, comprising: a hydraulic actuator; at leastone housing; and a self-contained hydraulic supply system positionedwithin said at least one housing, said self-contained hydraulic supplysystem comprising: a pump driven by an electrical motor; at least onefluid reservoir; and a control/vent valve.
 24. The modular actuator ofclaim 23, further comprising a control system positioned within said atleast one housing to control delivery of a high pressure hydraulic fluidproduced by said self-contained hydraulic supply system.
 25. The modularactuator of claim 23, further comprising a self-contained source ofelectrical power positioned within said at least one housing, whereinsaid self-contained source of electrical power is the primary source ofelectrical power for said modular actuator.
 26. The modular actuator ofclaim 25, wherein said self-contained source of electrical powercomprises at least one battery.
 27. The modular actuator of claim 23,wherein said modular actuator further comprises means for releasablycoupling said modular actuator to said subsea device.
 28. The modularactuator of claim 23, wherein said self-contained hydraulic supplysystem is adapted to supply a pressurized fluid employed in actuating asubsea valve.
 29. A modular actuator adapted to be releasably coupled toa subsea device, comprising: a hydraulic actuator; at least one housing;a self-contained hydraulic supply system positioned within said at leastone housing, said self-contained hydraulic supply system comprising: apump driven by an electrical motor; at least one fluid reservoir; and acontrol/vent valve; a control system positioned within said at least onehousing to control delivery of a high pressure hydraulic fluid producedby said self-contained hydraulic supply system; and a self-containedsource of electrical power positioned within said at least one housing,wherein said self-contained source of electrical power is the primarysource of electrical power for said modular actuator.
 30. The modularactuator of claim 29, wherein said self-contained source of electricalpower comprises at least one battery.
 31. The modular actuator of claim29, wherein said modular actuator further comprises means for releasablycoupling said modular actuator to said subsea device.
 32. The modularactuator of claim 29, wherein said self-contained hydraulic supplysystem is adapted to supply a pressurized fluid employed in actuating asubsea valve.